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    Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents.

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    Authors
    Lees, Nicholas P
    Harrison, Kathryn L
    Hall, C Nicholas
    Margison, Geoffrey P
    Povey, Andrew C
    Affiliation
    Cancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK.
    Issue Date
    2007-03
    
    Metadata
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    Abstract
    BACKGROUND AND AIMS: O(6)-alkylguanine DNA-alkyltransferase (MGMT) provides protection against alkylating agent-induced GC-->AT transition mutations. Such mutations are frequently seen in the KRAS oncogene of large colorectal adenomas, but whether adenoma or mutational risk in humans is influenced by MGMT activity and alkylating agent exposure is unclear. Hence, MGMT activity and, as an indicator of alkylating agent exposure, DNA-N7-methylguanine (N7-MeG) levels were determined in the normal tissue of patients with and without adenomas. METHODS: Biopsy specimens of normal colorectal mucosa were collected during colonoscopy from 85 patients with histologically proved colorectal adenomas (cases) and from 85 patients free of gastrointestinal neoplasia (referents) matched by age, sex and biopsy location. MGMT activity and N7-MeG levels were measured in colorectal tissue extracts and DNA, respectively. RESULTS: MGMT activity was higher in the normal mucosa of cases than in referents (6.65+/-3.03 vs 5.61+/-2.74 fmol/micro g DNA, p = 0.01). On stratification of cases, MGMT activity was found to be considerably greater in the normal mucosa of cases with large adenomas (p = 0.003) and slightly higher in cases with a GC-->AT transition mutation in the K-ras gene (p = 0.03). Elevated MGMT levels were associated with an increased risk of adenoma (OR 1.17, 95% CI 1.03 to 1.33 per unit increase in activity). Detectable levels of N7-MeG were found in DNA from 89% of cases and 93% of referents, with levels ranging from <0.1 to 7.7 micro mol/mol dG. Cases and referents had similar DNA-N7-MeG levels. CONCLUSIONS: Human exposure to methylating agents is widespread. MGMT activity is increased in the normal mucosa of patients with adenomas.
    Citation
    Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents. 2007, 56 (3):380-4 Gut
    Journal
    Gut
    URI
    http://hdl.handle.net/10541/73077
    DOI
    10.1136/gut.2006.097899
    PubMed ID
    16891355
    Type
    Article
    Language
    en
    ISSN
    0017-5749
    ae974a485f413a2113503eed53cd6c53
    10.1136/gut.2006.097899
    Scopus Count
    Collections
    All Paterson Institute for Cancer Research

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